Hello
I registered here hoping I would find an answer.
My problem started a while ago, when my pc occasionally would turn off without a warning and without any temperature problem. Recently it did more often + a new problem appeared, it was also powering itself on without any Wake-Up option activated in BIOS. Lastly, as soon as I plugged it in, all the fans would start running even though the power led on the front panel and the display remained turned off. Pressing the power button had no effect whatsoever, maybe just "speeding up" the fans when it was pressed. (tried with older "420w" no-name psu)

Should I just replace the PSU or there can be a problem with the mobo or cpu also?

i dont know about your psu maybe yes 80% sre but ihad same problem on older computer with the Power button in front case. it was dirty and stuck in middle contact..opening and closing computer sometimes by itself.

agree with MohawkAngel. try taking off the power button pins, and manually turn on the computer with shorting both the power pins.if it is indeed that is the problem, cleaning the power button on the case with contact cleaner.if that doesn't work, swith the power button with reset, so you had to press reset to power the pc.just dont plug the old power button back.leave it unplugged

agree with MohawkAngel. try taking off the power button pins, and manually turn on the computer with shorting both the power pins.if it is indeed that is the problem, cleaning the power button on the case with contact cleaner.if that doesn't work, swith the power button with reset, so you had to press reset to power the pc.just dont plug the old power button back.leave it unplugged

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Well said. But I got a trick for old switch. Clean them toroughly under hot water with cleaning stuff like Hertel. Then rinse it proerly and dry it with hair dryer. When its done drip some olive oil inside the switch and push it many times until it moves freely. Olive oil is often used as test coolant because guy swubmerged their motherboard in olive oil and its non-conductive.
I made it with older switches believe me

Well said. But I got a trick for old switch. Clean them toroughly under hot water with cleaning stuff like Hertel. Then rinse it proerly and dry it with hair dryer. When its done drip some olive oil inside the switch and push it many times until it moves freely. Olive oil is often used as test coolant because guy swubmerged their motherboard in olive oil and its non-conductive.
I made it with older switches believe me

Hello
I registered here hoping I would find an answer.
My problem started a while ago, when my pc occasionally would turn off without a warning and without any temperature problem. Recently it did more often + a new problem appeared, it was also powering itself on without any Wake-Up option activated in BIOS. Lastly, as soon as I plugged it in, all the fans would start running even though the power led on the front panel and the display remained turned off. Pressing the power button had no effect whatsoever, maybe just "speeding up" the fans when it was pressed. (tried with older "420w" no-name psu)

Should I just replace the PSU or there can be a problem with the mobo or cpu also?

Click to expand...

Other says "Get a new CPU or new PSU" but before you do that, try to set your BIOS into default setting, and if problem still occurs, change your PSU.

Burning PCB is no good. It looks like it's attached to the switching circuits. When those don't do their job, that overheating can happen. Swap the PSU as soon as you can. Hopefully, it hasn't compromised the integrity of any of the components. *Knocks on wood for Lepper*

I'll admit, I'm a little nervous about the fact that your motherboard is powering up the fans even though the system isn't running. That's not a symptom you want to be seeing. Either way, you should still replace the PSU. You don't want to connect it to a good replacement motherboard.

Tried with a good psu this time. Same crap: the fans start on their own and the leds + display don't light up. Is it the cpu or the mobo?

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By now, and reading what has been said, I would say the mobo is bad. Not sure what, maybe some short circuit in there.
Check the back side of the board to see if there is something (dust, a smudge or even solder) that could be shorting the power button pins.
That could help...If you haven't checked it yet.